As has been extensively documented, one of the leading nutritional problems in the United States today is obesity, which results from a consumption of calories in excess of those expended. A reduction of caloric intake can be significantly enhanced by a reduction in the intake of dietary fat, since fats provide approximately nine calories per gram as compared to four calories per gram provided by carbohydrates or protein. Studies have shown that fats contribute, on average, 30% to 40% of the total calories consumed by Americans [See e.g., H.L. Merten, J. Agr. Food Chem; 18:1002 (1970)]. Moreover, not only are dietary fats high in calories, but certain fats, consumed in large amounts, have been associated with heart disease and other problems.
Dietary fat is digested to free fatty acids and monoglycerides, primarily in the small intestine. The alpha-lipase steapsin cleaves the glycerol esters at the first and third positions, resulting in fatty acids of 6 to 10 carbon atoms and unsaturated fatty acids which are rapidly absorbed, while those of 12 to 18 carbon atoms are absorbed more slowly. Beta-monoglycerides are also absorbed in the small intestine. Approximately 95% of the total dietary fat is digested and absorbed in the small intestine.
Reducing fat consumption in the population at large, while highly desirable, is not easily achieved due to the fact that dietary habits are well entrenched. As such, much effort has been expended in recent years to develop low caloric fats or fat substitutes.
Several approaches have been taken to develop low calorie fat substitutes. One such approach is to reform the structure of natural triglycerides to retain their conventional properties in foods, while eliminating their tendency toward hydrolysis or subsequent absorption during digestion. For example, U.S. Pat. Nos. 3,579,548 and 4,582,715 disclose replacing the fatty acids attached to glycerol with alternate acids. Another example is U.S. Pat. No. 4,861,613 which discloses inserting certain groups between the fatty acids and glycerol.
Another approach in developing low calorie fat substitutes has been to synthesize minimally or non-absorbable polymeric materials which, although being structurally dissimilar from triglycerides, possess physical properties similar to edible fat. For example, U.S. Pat. No. 519,980 discloses the use of mineral oil as a substitute material. Other examples include U.S. Pat. No. 4,631,196 which discloses a polydextrose substitute, U.S. Pat. No. 3,876,794 which discloses both polymaltose and polyglucose substitutes, European Application No. 205,273, which discloses the use of a polysiloxane and East German Patent No. 207,070 which suggests the use of polyethylene polymeric materials.
A third approach explores the use of various polyol esters, that is, compounds which have numbers of fatty acid groups in excess of the three found in conventional fat triglycerides, as non-absorbable fat replacements. For example, U.S. Pat. No. 3,637,774 discloses certain polyglycerol ester substitutes. U.S. Pat. No. 4,582,927 describes synthetic cooking oils containing dicarboxylic acid esters useful as low calorie synthetic oils suitable for consumption by mammals.
As mentioned above, U.S. Pat. No. 519,980 has described the use of mineral oil as a polymeric, minimally absorbable low calorie fat substitute. Petroleum-based white mineral oils are highly refined, water-white products made from lubricating oil distillates. These oils are complex mixtures of saturated hydrocarbons including straight chain, branched, ring structures and molecules containing all three configurations. White mineral oils typically have carbon numbers in the C.sub.15 through C.sub.30 range.
The relative number of saturated ring structures and straight or branched chain structures will determine whether the oil is characterized as naphthenic or paraffinic in nature. White mineral oils are obtained from the intensive treatment of a petroleum fraction with sulfuric acid or oleum, by hydrogenation, or by a combination of sulfuric acid treatment and hydrogenation. The petroleum fraction is obtained by atmospheric and vacuum distillation to isolate the desired boiling range and viscosity and then solvent treated and dewaxed to remove polar compounds aromatics and waxes.
While mineral oils are likely to be suitable for use as a low-calorie fat substitute in frying and cooking oil and for food use, there has been in recent years concern over the potential risk to human health arising from the use of petroleum-derived mineral oils as food additives and food lubricants. In February 1989, the United Kingdom Ministry of Agriculture, Fisheries and Food recommended a ban on virtually all food applications of mineral hydrocarbons, including white mineral oils. The United Kingdom decision was based in large part upon toxicological findings reported recently with white oils in rats by the industry [P. Watts, Mineral hydrocarbons in food-a ban?, BIBRA Bulletin, 28: 59-65, (1989)]. Repeated administration of conventional white oils in the diet (over 90 days) has been found to lead to the accumulation of oil droplets in the lymph nodes, liver, spleen and other target tissues in the animals. At high doses, this is accompanied by granuloma formation that is considered to be toxicologically important. Hematological and clinical chemistry abnormalities were also observed in these studies which are indicative of probable adverse health effects. While many other animal studies have not produced similar effects and there have been only rare indications of adverse effects in humans despite the many years in which mineral oils have been used in food and medicinal preparations (e.g., laxatives), the use of petroleum-based products is expected to come under continued scrutiny. Concern over the health safety of white mineral oils indicates a need to consider alternative hydrocarbon materials such as synthetic polyalpha olefins as suitable non-toxic substitutes.
Because of the polymeric nature and the high molecular weight of hydrogenated polyalpha olefin materials, these synthetic oils are not expected to be readily absorbed when ingested orally. Digestion of these materials by intestinal lipasee is not expected since these materials are hydrocarbon-like in nature and lack ester functional groups. Moreover, the low absorbability of these materials is likely to be an important factor governing their safety and the absence of adverse effects. The minimal absorbability of hydrogenated polyalpha olefins also diminishes the likelihood of accumulation in the tissues and therefore reduces the chances of adverse effects (e.g., granuloma formation) in the tissues, thus leading to a safe, non-toxic and low caloric product. The notion of minimally absorbable or non-absorbable polymeric food additives and fat substitutes have been documented in the literature [J.P. Brown and T.M. Parkinson, Non-absorbable food additives through polymeric design, Drug Metabolism Reviews, 16: 389-422 (1985); R.J. Jandacek, Developing a fat substitute, ChemTech, 398-402 (July 1991)]and represents a rational approach towards developing safer substances for use in food and nutrition. There exists a need to apply this concept toward developing suitable synthetic hydrogenated polyalpha olefins that have use as a low-caloric and minimally absorbable and minimally digestible cooking and frying oil and fat substitute.
In addition, another important consideration in the development of synthetic cooking and frying oils is the boiling point of the synthetic material. While many of the above mentioned low calorie fat substitutes possess desirable characteristics when used at room temperature, they are not suitable as cooking and frying oils. For example, esters of malonic acid, and low molecular weight alcohols are known but are unsuitable for use as vegetable oil substitutes due to their low boiling points.
Therefore, there exists a need for temperature-stable, polymeric synthetic oils which are not readily digestible and not readily absorbable and which are suitable for use in the production of low-calorie fried and baked foods.